The sensor is S1 in this alarm that we found in a Radio Electronics magazine from May 1971. Several sensors can be used in series. The SCR supports equivalents from the 106 series.
The critical component of this 1967 amplifier is the driver transformer. The circuit has both high...
This transistor tester configuration can be found on this website with many variations. The...
This circuit is from 70's documentation. The output transistors can be BC548 and BC549. The driver...